The present invention relates to medical tubes, such as, for example, nasogastric and nasointestinal feeding tubes, and particularly the confirmation of correct placement and/or avoidance of misplacement of the portion of the tube through which the fluid exits.
In healthcare, human or animal patients may be incapable of feeding themselves by conventional means. In such circumstances it is necessary to deliver nutrients into the stomach or small intestine by way of a feeding tube. This is generally carried out by passing a tube through the patient's nasal passage and into the stomach or the small intestine by way of the gastrointestinal tract. The distal end of such feeding tubes comprise one or more fluid output apertures, which act to deliver fluid nutrients to predetermined locations such as, for example, the stomach or small intestine. Correct positioning of the fluid output apertures within the stomach or small intestine is essential for the safety of the patient. For example, misdirection of the feeding tube upon insertion via the nasal cavity such that the leading end of the feeding tube is directed towards the lungs may occur, particularly with patients who have an inhibited cough or gag reflex such as, for example, the critically ill and premature babies. Such misplacement of the fluid output apertures may, upon feeding, lead to serious pleuropulmonary complications such as, for example, pneumonia, abscess and empyema.
Also, in certain circumstances it may be necessary for certain fluid nutrients are delivered to specific parts of the digestive system such as, for example, specifically to the stomach and/or specifically to the small intestine. Again, correct placement of the fluid outlet apertures is essential.
Generally, health practitioners currently approximate for the position of the fluid output apertures before confirming the correct position.
A commonly used method for approximating correct placement of the fluid output apertures is to connect a syringe to the proximate end of a pre-placed feeding tube and aspirate a quantity of fluid from the region around the fluid output apertures. The pH of the aspirated fluid is then measured using pH paper to determine whether, for example, the pH of the fluid corresponds with the pH of gastric fluid from the stomach thereby confirming placement of the fluid output apertures in the stomach. This method is currently recommended by the National Patient Safety Agency (NPSA) in the United Kingdom for use in the UK National Health Service (NHS), in addition to confirmation using X-Ray if the pH test is inconclusive.
Despite the publication of the NPSA recommendations, there has remained an unsatisfactory number of deaths and harm due to misplaced NG feeding tubes occurring in the NHS. Moreover, the cases of misplaced NG feeding tubes has not only been as a result of the bedside procedure but also from the misinterpretation of X-Rays [National Patient Safety Agency (NPSA): Patient Safety Alert; NPSA/2011/PSA002].
The NHS considers misplaced NG feeding tubes to be such a problem that it has been listed on the NHS “Never Events” list since it was first introduced in 2009 [NPSA; Never Events Framework 2009/10, page 5].
The NHS is consistently monitored and managed for best practice. However, such monitoring and management does happen in most countries throughout the world. Consequently, it is envisaged that the number of deaths and harm caused by misplaced feeding tubes is at least proportional to that of the NHS and probably greater.
The currently NPSA recommended pH test is disadvantaged for a number of reasons. It is often difficult to obtain sufficient fluid by aspiration to carry out the test, which can distress the patient and result in delayed feeding which is detrimental to the wellbeing of the patient. The quality of the test is relative to the competence, diligence and interpretation of the individual health professional undertaking the test. It is known for the aspirated gastric fluid to become contaminated as it is transferred from the syringe to the pH paper, leading to false readings. Furthermore, significant care has to be taken not to aspirate too much fluid. Also this method can be unpleasant for the patient as it can tend to induce reflux and vomiting which can lead to further complications. Where the pH test is inconclusive, the patient cannot be fed and X-Ray must be used to confirm correct placement. However, X-Ray is relatively expensive, as it requires a radiographer, X-Ray equipment and also a doctor to confirm correct placement. Moreover, recent studies have shown that a high number of misplaced feeding tubes have been missed due to misinterpretation of X-Rays. Furthermore, this method is further disadvantaged in that the patient, who may be critically ill, may also have to be transferred to a radiology department and is also exposed to X-Ray.
Another method, which the NPSA has specifically recommended should not be used, is the so-called woosh method, which involves using a syringe to inject air into the proximate end of a pre-inserted feeding tube. The health practitioner then listens using a stethoscope around the stomach region for a wooshing noise to confirm the fluid exit apertures of the tube are located in the stomach. However, although widely used outside the United Kingdom, studies have shown that the woosh test does not provide sufficient accuracy of confirmation that the fluid exit apertures of the tube are actually in the stomach when the woosh noise can be heard by the health practitioner. Patent document number U.S. Pat. No. 5,085,216 describes a feeding tube assembly for nasogastric and nasointestinal feeding comprising a pH indicator carried by a stiffener used for inserting the feeding tube into a patient. After insertion of the leading end of the feeding tube into an approximated desired position the pH indicator is withdrawn and examined for a pH corresponding to that of the stomach thereby indicating that the end of the tube is positioned in the stomach. However, this feeding tube assembly is disadvantaged in that it is necessary to approximate the correct position of the tube prior to withdrawing the pH indicator to determine whether or not the tube is correctly positioned. If the tube is not correctly positioned in the stomach it is necessary to withdraw the tube from the patient and repeat the whole procedure again using a complete new feeding tube assembly which is undesirably wasteful, time consuming and distressful for the patient Furthermore, the pH indicator may become contaminated as it is withdrawn into the environment external to the body leading to false and unreliable pH readings.
Patent document number U.S. Pat. No. 4,381,011 discloses a system and method for feeding of fluid into a preselected portion of the gastro intestinal tract of a patient. The system comprises a tube with a pH measuring device positioned thereon, a monitoring device, capable of processing pH signals to determine the position of the tube, and a fluid feed control. Initial positioning of the tube and subsequent monitoring of the position of the tube is accomplished by receiving and processing pH signals from the pH measuring device positioned proximate the distal end of the tube and connected to the monitoring device. The tube may be selectively positioned in a preselected portion of the digestive system by monitoring the pH, which the pH measuring device is measuring, and comparing those measurements with known values of pH for specific portions of the digestive system. However, this system is disadvantaged in that it is relatively expensive, needing pH measuring devices and monitors, and requires an external electrical power supply.
Patent document number EP2412311A2 describes a feeding tube position confirmation device having an input optical waveguide and an output optical waveguide dimensioned to be insertable into the lumen of a feeding tube. A sensor is disposed on the optical waveguides at a position which corresponds to the predetermined portion of the feeding tube. The sensor means has a colour change indicator operable to change colour relative to the chemical content of the environment proximate thereto. In use, the input optical waveguide carries light to the sensor means. The sensor means causes a change in the colour of the input light to provide an output light of a predetermined colour indicative of the position of the feeding tube. The output light is carried to the proximate end of the position confirmation device, by the output optical waveguide, at which it is viewed by the user to determine the position of the tube in the human or animal body.
Although this device is relatively simple, it is relatively difficult to manufacture in a repeatable manner in that it is difficult to form a robust and repeatable colour sensor disposed on the end of the input and output optical waveguides. Moreover, unless a robust and strong attachment is able to be established between the optical waveguide and the sensor there is a danger that in use, the sensor may become detached from the waveguide. Also, both an input and output optical waveguide is required in order to return sufficient light from the sensor to the proximate end of the position confirmation device. This is particularly disadvantageous because the diameter of the device needs to be as small as possible in order to be applicable to all sizes of NG feeding tube, including small French size tubes.
It is therefore desirable in the industry for there to be a feeding tube position confirmation device which is easy to use, robust, reliable, applicable to all sizes of tubes, relatively inexpensive to manufacture and capable of indicating correct positioning of a tube during insertion of the tube, and which does not require an electrical mains power source.